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Catalyst for hydrodechlorination of chlorosilanes to hydrogen silanes and method for implementing hydrogen silanes using said catalyst

a technology of chlorosilane and hydrogen silane, which is applied in the direction of physical/chemical process catalysts, metal/metal-oxide/metal-hydroxide catalysts, silicon compounds, etc., can solve the problems of increasing the energy requirement of the process and thus the cost, uneconomical processes, and significant amounts of by-products

Inactive Publication Date: 2012-06-14
WACKER CHEM GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention aims to improve the process of hydrodechlorination of chlorosilanes using molecular hydrogen. The invention provides an economically and universally applicable process that can be carried out at industrially handleable temperatures. The invention involves the use of a catalytic amount of elemental zinc in a support composed of metal oxide. The reaction of any chlorosilanes with hydrogen gas in the presence of the catalyst results in the formation of hydrogensilanes.

Problems solved by technology

Disadvantages of this process are the significantly higher proportion of hydrogen in the reaction gas and the quench by means of a liquid which is employed, both of which greatly increase the energy requirement of the process and thus the costs.
It is common to all these known processes that they operate at very high temperatures or use stoichiometric amounts of chloride scavengers or the coproducts and by-products obtained or the use of metal and salt melts which are problematical in process engineering terms make the processes uneconomical or, particularly in the case of stoichiometric reactions, significant amounts of by-products are formed.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Hydrodechlorination of Tetrachlorosilane

[0029]30 g of pyrogenic silica is dispersed in 70 g of distilled water and metallic zinc corresponding to a proportion of 1% by weight based on the total solid is added to the composition. The composition is subsequently extruded to form extrudates and dried. 10 g of the dry catalyst are introduced into a tube reactor and firstly treated with hydrogen at 500° C. for hours. A mixture of 20% by volume of tetrachlorosilane in hydrogen is passed over the catalyst at 450° C. at a GHSV of 625 per hour and the composition of the exiting product mixture is determined by gas chromatography.

[0030]The amount of trichlorosilane formed is significantly above that corresponding to a stoichiometric reaction of 2 mol of SiHCl3 per mole of zinc. A TON (turnover number) of 225 was achieved up to the end of the experiment after about 48 hours.

example 2

Hydrodechlorination of Methyltrichlorosilane

[0031]30 g of pyrogenic silica is dispersed in 70 g of distilled water and metallic zinc corresponding to a proportion of 1% by weight based on the total solids is added to the composition. The composition is subsequently extruded to form extrudates, cut and dried using a ram extruder. 10 g of the dry catalyst are introduced into a tube reactor and firstly treated with hydrogen at 500° C. for 2 hours. A mixture of 20% by volume of methyltrichlorosilane in hydrogen is passed over the catalyst at 450° C. at a GHSV of 625 per hour and the chemical composition of the exiting product mixture is determined by gas chromatography.

[0032]At a theoretical stoichiometric conversion, a maximum of 2 mol of dichloromethylsilane would be formed per mole of zinc. The results show a significantly superstoichiometric formation of methyldichlorosilane as reaction product of the hydrodechlorination of methyltrichlorosilane, corresponding to a TON of 120 to con...

example 3

Hydrodechlorination of Methyltrichlorosilane

[0033]30 g of pyrogenic silica is dispersed in 70 g of distilled water and catalytically active metals corresponding to the following table in % by weight based on the total solids is added to the composition. The composition is subsequently extruded to form extrudates and dried. 10 g of the dry catalyst are introduced into a tube reactor and firstly treated with hydrogen at 500° C. for 2 hours. A mixture of 20% by volume of methyltrichlorosilane in hydrogen is passed over the catalyst at 450° C. at a GHSV of 625 h−1 and the chemical composition of the exiting product mixture is determined by gas chromatography. The results are shown in the form of the steady-state yields in the following table.

Active component(s)Yield25% by weight of Zn8.4%50% by weight of Zn2.7%75% by weight of Zn1.0%12.5% by weight of Zn, 12.5% by weight of Cu10.0%

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Abstract

The invention relates to a method for producing hydrogen silanes of general formula RnCl3-nSiH by converting chlorosilanes of general formula RnCl4-nSi, where R, in both formulas simultaneously and independently of each other, is a hydrogen atom, an optionally substituted or unsubstituted hydrocarbon radical having 1 to 18 carbon atoms, and n can have the value of 1-3, and hydrogen gas in the presence of a catalytic quantity (K): zinc and / or an alloy comprising zinc on a metal oxide carrier.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the national phase filing of international patent application No. PCT / EP2010 / 061780, filed 12 Aug. 2010, and claims priority of German patent application number 10 2009 028 653.5, filed 19 Aug. 2009, the entireties of which applications are incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention relates to a process for preparing hydrogensilanes by catalytic hydrogenation of chlorosilanes by means of hydrogen gas in the presence of a heterogeneous catalyst based on metallic zinc and also to the catalyst.[0003]The process of the invention is, for example, suitable for the hydrodechlorination of the tetrachlorosilane obtained in large quantities in the preparation of pure silicon to trichlorosilane, with the latter being able, for example, to be reused for the deposition of silicon or be reacted further by the process of the invention to form its homologues dichlorosilane, chlorosilane and monosilane.[...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C07F7/14B01J23/80B01J21/08C01B33/107B01J23/06
CPCB01J21/08B01J23/06B01J23/80C07F7/126B01J37/04B01J37/18C01B33/1071B01J37/0009C07F7/12C01B33/107
Inventor ZIPP, ALEXANDEREBERLE, HANS-JURGEN
Owner WACKER CHEM GMBH